I also might need an external heat source to warm me, especially if laying down. I try not to go to bed cold, as I cannot fall asleep when cold (I also can't sleep if much hot, heh). If I have the energy, a warm shower (with shower chair) helps.
Once lying down, I use lightweight breathable but warm covers. I like wool, which is also supposed to be resistant to dust mites. Once, I got a fantastic never-seen-again sale on a wool duvet and washable wool blankets.
I used to use an electric heating pad, but this now triggers neuropathic pain (heat, mostly, but it can be uncomfortable and even prickly, especially when brought on by the heating pad, and I was once told: "If you don't like it and want it to stop, that's pain." --when I was conflicted about reporting stuff as "pain" at physical therapy, because it was uncomfortable but didn't fit my definition of pain)
I think one year I used
lemon essential oil (I used a few drops in another oil), which was supposed to increase circulation, and it actually worked to warm my feet.
My thyroid tests are all fine, and I do not fit neatly into a hypothyroid profile.
If I'm sitting up, I use throw blankets, sweaters, whatever is handy. Also those instant hot hand warmers. I have a reusable one somewhere.